Remote control devices are used widely in the home and in industry for operation of appliances and equipment and in access and security systems. A popular use of such devices is to operate doors, gates, lights and security systems. It is particularly desirable to employ a remote control device within a vehicle to control such devices without exiting from the vehicle. One of the most widely used of these applications is the use of a remote control transmitter/receiver system to control garage doors to allow entry or exit of a vehicle. Remote control devices used out-of-doors, such as those used for access to doors or gates, typically employ UHF radio transmission.
In general, a remote control system has a remote transmitter and a receiver coupled to the device which is to be controlled. When activated, the transmitter emits a modulated signal which is recognized by the receiver which then activates the device in response to the transmitted signal. In UHF-based systems, a transmitter typically emits a pulse-modulated UHF signal. The signal embodies a modulation pattern as a sequence of "signal on" and "signal off" intervals. The modulated signal emitted by the transmitter is recognized by the receiver.
The modulation pattern of remote controls used for access to garages, homes and businesses or for security systems is typically unique to restrict unauthorized access to the device being controlled.
For convenience of use with access and security devices, it is desirable to have a remote control within a vehicle. Presently this is accomplished for the most part by carrying a portable battery-powered remote control transmitter supplied by the device manufacturer in the vehicle. Often such portable transmitters are clipped to visors, or left loose on dashboard and seats. A variety of means for holding such portable transmitters within a vehicle are available. However, the car owner must go to the trouble of installing the holder and then inserting his portable transmitter in the holder. Further, all such holders are still susceptible to easy removal from the vehicle. The security of an in-vehicle remote control transmitter can be maximized by employing a permanently installed transmitter which, for example, is not readily removed from the vehicle. Further, permanent factory installations allow improved ergonomics and esthetics inside the vehicle. For example, the transmitter actuator switch can be conveniently located on the dash or steering column allowing easy access for the driver, and unobtrusive bending with the vehicle's interior decor.
Permanently installed remote controls have been offered as buyer option on new cars, for example, but a purchaser of this option must also purchase a receiver compatible with the installed transmitter or purchase an adapter for his existing receiver to make it compatible with the installed remote control transmitter.
Different manufacturers of UHF remote control systems use different frequencies for transmission as well as different modulation protocols. For example, the length of the on/off intervals in a pulse modulation protocol will vary from manufacturer to manufacturer. In order to obtain a UHF transmitter compatible with an existing receiver, it is necessary to know the transmission frequency accepted by the receiver and have a means for matching or determining the modulation pattern recognized by the receiver. In a number of UHF transmitter/receivers, the modulation pattern is determined by a set of dip switches on the transmitter and receiver. Once the required frequency and the modulation protocol are defined, a compatible new transmitter can be obtained, and dip switches or other modulation pattern selection means can be employed to match the pattern transmitted by a new transmitter to that of the existing receiver. Alternatively, both the existing receiver and new transmitter can be programmed with a new modulation pattern. Such means for programming a transmitter/receiver with a modulation pattern is not universally applicable to all UHF remote control systems. Further, such means as dip switches change only the modulation pattern and cannot be adapted to different modulation protocols. It may not be desirable for security reasons to employ dip switches to set a modulation pattern, since the pattern can be determined by examination of the dip switch pattern of a transmitter. It may not be desirable to employ a transmitter whose modulation pattern can be inadvertently changed by accidental modification of the dip switch pattern or changed by unauthorized access to the dip switches or other pattern selection means.
Means for programming a transmitter to transmit the modulation pattern of an existing programmed transmitter or to transmit a modulation pattern recognized by a receiver are known. However, these methods require prior knowledge of the frequency of transmission and modulation protocol and require the use of compatible transmitters and receivers. These methods also require the use of more complex transmitters and/or receiving systems. The transmitter to be programmed must also have a receiver for receiving a modulated signal and circuitry for demodulating the signal to determine the modulation pattern in addition to a memory for storing the modulation pattern. In some cases the receiver which activates the device must also be capable of transmitting a modulated signal.
To minimize cost and maximize convenience of manufacture for a transmitter, particularly when it is to be permanently installed in a vehicle as a factory installed option, it is desirable to employ a transmitter that can be programmed to replace the widest variety of existing remote control transmitters. The device should be programmable for any legal UHF frequency and compatible with any modulation scheme. Since all currently manufactured UHF remote control systems employ some kind of pulse modulation protocol, the preferred transmitter must be capable of functioning to emit a pulse-modulated UHF signal.
Means are known in the art for determining the frequency transmitted by a remote control transmitter and means are known for tuning a transmitter to a frequency transmitted by another transmitter. Means are also known for determining the pulse-modulation pattern emitted by a transmitter.
For example, means are known in the art for matching the carrier frequency/modulation pattern transmitted by an Infra-red-based (IR) remote control transmitter in a second IR transmitter. See, for example, U.S. Pat. No. 4,623,887 to Welles and U.S. Pat. No. 4,825,200 to Evans et al., both teaching a microprocessor-based IR remote control unit including an IR transmitter and an IR receiver for receiving signals from another remote controller to be emulated.
In contrast to modulated IR transmission, it is more difficult to determine the frequency and modulation pattern of a UHF pulse-modulated signal, and, as a consequence, relatively expensive devices are required to do this.
The programming system of the present invention produces the desired result of a universal transmitter capable of being programmed to function with most existing UHF receiver/devices (and all currently manufactured UHF receivers) at a relatively low cost which does not require the purchase of additional receivers or adapters and does not require owner installation.